In answer to Dean's question, we use GASLIGHT rules with the Battles by GASLIGHT supplement in order to simplify the large battles we play.
The original GASLIGHT rules are really only designed for fairly small games - typically each side player having no more than 1 or 2 each of troop units, vehicles and independant main characters. Due to the card-based order of movement system and multiple die rolls required for the game, any more than this can cause the game to bog down (especially if multiple players are involved).
Battles by GASLIGHT has 4 main features that simplify/improve play:
1 - The card-based movement system changes to 1 card per command of 1 leader and up to 4 troop/vehicle elements, thus speeding up movement a lot.
2 - For failed unit morale you roll the effect for all unit members (in the original rules you roll separately per figure).
3 - New vehicle hit effects table. The generic Hit Table in the original rules applies to all vehicle types, with separate columns for the effects of Non-Penetrating, Penetrating and Catastrophic hits. The Hit Table in Battles has separate columns for Wheeled/Tracked vehicles, Walkers and Flyers, with only one effects column per vehicle type. With this table you get more applicable results for the affected vehicle.
4 - Rather than using one die per unit member shooting or attacking in melee, Battles has a very good combat table wherin you make one roll for all firers/attackers in a unit who have the same weapon and SHOOT/SCUFFLE roll. This reduces die rolls a lot and works very well. It can also be used where multiple unit members need to make SAVE rolls or START/ SUSTAIN rolls (e.g. for my Prussian luftreiter helicopter troops).
1, 2 and 3 above also work very well with normal GASLIGHT games.
Other than using the above rules, we have also used the rules within Battles for vehicle overrun attacks on troops, vehicles ramming each other and troops attacking vehicles with bombs (having played with these a couple of times we will be modifying these rules to suit our style of play). Battles also has rules for repairing vehicles in battle, but we have yet to explore these. As per my comments above, these additional rules are all compatible with normal 'small' games using the core GASLIGHT rules.
The other main feature of the Batltes rules is the inclusion of Leviathans by GASLIGHT (rules for very large vehicles). We have yet to try these rules, so I can't provide any feedback on them at the moment.
For anyone playing GASLIGHT the Yahoo group is highly recommended, as it is moderated by the guys who wrote the rules and is a good place to discuss problems with the rules or suggestions for things outside the rules. As Dean said, the Yahoo group is a bit quiet at the moment, but I'm sure that with a few posts we can wake them up!
http://games.groups.yahoo.com/group/GASLIGHTrules/For those of you who are Yahoo group members, I have posted the playsheet and vehicle stats we used for the Prussian Invasion games in the files section on the group (see folder called House Rules).